Pwn20wnd’s unc0ver jailbreak tool supports all iOS versions from iOS 11.0-12.1.2 and most iOS devices in between, but it only partially supports A12(X) devices at the time of this writing because of reasons that we outlined in a piece published earlier this week.
Two of the most significant roadblocks that have prevented a full-fledged A12(X) jailbreak from surfacing are that Cydia Substrate needs to be updated with compatibility for these devices and that Pwn20wnd still needed to update Unrestrict library for sandbox patches on arm64e devices. Fortunately, the latter is no longer a problem as of today.